1. Field of the Invention
This invention relates to photographic cameras and, more particularly, to photographic cameras providing electronic flash illumination.
2. Description of the Prior Art
The use of transient artificial illumination such as from incandescent flash bulbs or electronic strobe units for providing scene illumination for photographic exposures under conditions of low ambient scene light intensity, are well known in the art. Examples of camera systems which utilize strobe illumination under low ambient conditions are described in U.S. Pat. No. 4,007,469 granted on Feb. 8, 1977 to Edwin H. Land, et al; U.S. Pat. No. 4,086,606 granted to Patrick L. Finelli, et al. on Apr. 25, 1978; U.S. Pat. No. 4,085,414 granted on Apr. 18, 1978 to John P. Burgarella, et al; and U.S. Pat. No. 3,438,766 granted on Apr. 15, 1969 to Conrad H. Biber.
Additionally, the use of transient illumination during an exposure under higher ambient scene illumination for fill-in flash are also well-known in the art. In the latter case, the transient illumination is generally employed, not as the primary illumination for exposure, but rather as supplementary to the ambient illumination so as to add foreground illumination of the subject, soften shadows, or to generally increase the subject illumination.
In many fill-in arrangements, the camera operator manually selects the use of fill-in flash and the proper exposure parameters which determine the relative effectiveness of the transient illumination and the ambient illumination. Examples of such fill-in flash systems are described in "Flash Fill-in", page 58, Practical Photography, October, 1978; U.S. Pat. No. 4,079,389 issued Mar. 14, 1978 and in U.S. Pat. No. 4,023,187 issued May 10, 1977.
The latter patents both describe camera systems which will operate in a fill-in flash mode when a flash accessory is mounted on the camera. The camera described in U.S. Pat. No. 4,079,389 requires manual selection of the degree of flash exposure, while U.S. Pat. No. 4,023,187 automatically determines the latter. Consequently, at least in the latter case, mere mounting of the flash unit on the camera under normal scene light conditions provides selection of the fill-in flash mode. However, the operator must still make a deliberate selection of this mode and often, either forgets to make use of this fill-in flash arrangement, or deliberately avoids use of the latter; perhaps for reasons of economy and a lack of understanding or appreciation of the value of fill-in flash. Hence, while the prior art suggests using transient illumination under varying conditions of scene illumination, the determination of whether to use transient illumination in addition to the normal scene illumination is generally left to the decision of the operator. Consequently, it is an object of this invention to provide a photographic camera automatically employing improved exposure control under substantially all conditions of ambient scene illumination.
A further object is to provide a fully automatic strobe camera which will automatically provide strobe illumination under all scene lighting conditions at least when the subject is within range of the strobe illumination. Another object of this invention is to provide a fully automatic strobe camera utilizing a film cassette and battery combination configured to automatically fire a strobe flash during all or substantially all camera exposure operations.